New heterobimetallic complexes of nickel, palladium or platinum and the ligand cis-l,2-bis(diphenylphosphine)-ethene, dppen, and tin were prepared. The transition metal is bonded either directly or via chlorine bridges to the tin atom. The compounds were obtained from precursor complexes of the general formula [M(dppen)Clz] (M = Ni, Pd or Pt) by reaction with Ph3SnH or SnC12.
nickel Summary This paper describes a series of bimetallic compounds derived from the starting complexes [Ni(tdpme)C12] and [Pt(tdpme)C121 [where tdpme = 1,1,1-tris(diphenylphosphinemethyl) ethane, MeC (CH2PPhz)3] upon reaction with Ph3SnC1 and NaBH~, as well as with SnC12. In the first case, a direct bond between tin and the transition metal is formed (with concomitant reduction to the 1 + oxidation state for the nickel species), whereas SnC12 forms chlorine bridges with the transition metals.
The preparation of eight new complexes of Cr III and VO w with urea derivatives is reported here. The ligands used were 2-imidazolidinone (ethyleneurea, EU), N,N'-dimethyl-2imidazolidinone (N,N' -dimethylethyleneurea, DMEU), 2imidazolidinethione (ethylenethiourea, ETU), and(tetramethylurea, TMU). The previously reported complex VOC12(TMU)2 was also prepared. All nine complexes were investigated with regard to conductimetry as well as visible and i.r. spectroscopy. All carbonyl-containing complexes exhibit a metal-oxygen bond, whereas in ETU complexes a metal-nitrogen bond seems to be favoured. Results and DiscussionThe spectroscopic data are presented in Table 1. The complex [Cr(EU)6](NO3) 3 is likely to have Oh symmetry and one would expect the three absorptions of a d 3 type species: 4A2g 4T2g, 4A2g ~ Tlg, and 4A2o ~ 4Tlg(P ). The low E values are consistent with this model (~) but the third transition is hidden under an intense charge-transfer band. Equating the energy of the first absorption to 10 Dq and using the energy of the second absorption, one can calculate (2) the adjusted Racah parameter B' for [Cr(EU)6](NOB)3, which turns out to be 539 cm -1. Two other parameters can also be estimated for ethylene urea, namely J0rgensen's spectrochemical f factor (f = 0.96), and the nephelauxetic parameter h (h = 2.9) (3/. Ethylene urea is thus shown to be above urea and below water in the spectrochemical series; its nephelauxetic parameter is, however, well above those for both molecules. The other EU complexes in Table 1 present similar absorption energies and molar absorptivity values, and their expected tetragonal distortions are not readily apparent from the spectra. The same occurs for the other Cr III complexes, [Cr(DMEU)2 (H20)2C12]C1 9 H2O and [Cr(ETU)4(H20)2](NO3)3.3 H20 , suggesting that the fields due to DMEU and ETU are similar in strength to that of EU. The oxovanadium(IV) complexes 1 (4 8) contain a d species which has been extensively studied -. Assuming a C4v model, three bands could be expected, but the high energy one is only observed as a very broad and intense u.v. band. According to the clustered level scheme, (6-8) the transitions are b2 ~ e*, b~' (ca. 13 000 cm-1), and b2 --* I a{ (ca. 17000 cm-1), followed by a charge-transfer absorption, e b b2 (ca. 25 000 cm-!). If [VO(ETU)s]C12 is assumed to have C4v symmetry, then the pentacoordinate species [VO-(TMU)2C12] and [VO(DMEU)2C12] ought not to deviate too much from the C4v model, for their absorptions are very close * Author to whom all correspondence should be directed.in energy to those of the former complex. [VO(EU)3SO4] , on the other hand, absorbs at considerably lower energies than the other three. Not only is the sulphate ion a totally different ligand but it also functions as a bidentate chelating group, as
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